Pump and motor hydraulic system and electrical control circuits therefor



Sept. 23, 1952 1 A, ACKERMAN 2,611,246

PUMP AND MOTOR HYDRAULIC SYSTEM AND ELECTRICAL CONTROL CIRCUITS THEREFOR Filed April 28, 1950 I' 'T'T' d :l i l 30\ $7/ IFI!! .alV`

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/24 /23 Jasf/JH A. AcKmMAA/A/ Patented Sept. 23, 1952 PUM'IEI AND MOTOR HYDRAULIC SYSTEBI AND ELECTRI'C'AL CONTBQL' CIRCUITS THEREFOR y. Joseph A. Ackermann, Cleveland `I-fleights, Ohio, l

assignor to The "Elvvell-Parker 4Electric ,Clnlpany, Cleveland, Ghio, a corporation of'Ohio Application April 28, 1950, .Serial 1N o'. 158,/81'1'4 's claims. (C1. sli-.52) e v. This-.inventionrelates to hydraulic Asystems and .controls therefor in industriallift trucks, and particularly to tilting lift .trucks of the roll clamping and roll rotating type, in bWhichthe clamping force is supplied by a hydraulic system. y

lAn .object of this invention is the p rvoyision'of Y a control system by which therload clamping` pressure is automatically/.maintained within a desired predetermined range, withoutv the necessity of continuous operation ofthe hydraulic" pump.y n

AAnother.,object is to l`providea .hydraulic lacti- 4vating system for a hydraulic clamp on a lift truck by whichv the clamping, onceinstituted, is vmaintained positivelyto .the .exclusion of the .in-

stitution of the clamp releasingr action, whenv the operator -leaves the truck.

stm further objects, .and advantages .win .ap-

.pear in thelfollowing description, .and drawing in which:

Fig. .l shows a preferred arrangement of hydraulic and electric circuits and controls fora roll clamp, activated and controlled .by thisinventicin;

yFigjf2 is the electric circuit of Fig.,1 presented independently for thesake of clarity.

For the .handling of paper rolls, drums and other cylindrical objects, thecommon .industrial 4truck-s of the tier .lift tutebiefremeytype have been provided with a roll clampingand .grasping I'ner'zlianism.V In addition vto .the truckbodyfand .chassis with the ordinary y electrical'ory mechanical .means for propulsion and steering, Vantiniechan'i'cal,r hydraulic or .electricalmeansioiftilting the; upright frame and raising and tlowering. the load @carriage carried :.by' `.the traine;` a'rota'table `clamp'is provided v,on 4the load `carriage.`, Tlie cl'anrprrotating mechanism, .whichy is interposed .between the load carriage and the 4vclamp proper,

Amay be electrically or hydraulicallyoperated,.its `main feature being rotatability through atleast so" soldier objects may be picked up from ahori- -zontal position and rotatedto the verticalin tiering, or vice-versa. The particular .forni .of` the clamp maybe .rather varied, but` almost .universally the rOll clamp comprisesjawswith curved njtericr f acessurfaced in wholelorinpart withrub'- bertior some other,` preferably resilient', .friction padding, and .a hydraulic cylinder. means` for 'opening vand closingthe jawsto apply or release clamping pressure.

.of [such aclamp. Since .the clamp Vcan beelevated with .a load .to aheight Well :above :the floor, .and e cylinders where. releasing, pressure is .tor heapcan be retained there, l,safety considerations@- Vmand, that the -possibilityof fslipping ,of .thevvrdll from .the clamp,.or.of accidental release, saywhen .the yoperatorie foi `the truck, ,be obviated.. Y'The presentinvention has features meeting these requirements in .the *form of a .dead-'man" control icrthe clamp releasing'action, vancljin.arneans for .yautomaticallyrestoring or maintaining the requi-k site clamp-ing pressure Without continuous-.operatonof they hydraulic'p'urnp.v in the .clamp circuit. Further, the'hydraulic circuit-of this invention is such as allo-ws the Iuse .free and quick acting -oil y control or oi1 reversing' valve. .Since it iis possible to usesuch ayalve, a solenoidlof reasonable size is suicient Cooperate it,so thattull electric control ofthe hydraulic.operation-ispossible.

. l .The hydraulic circuit system for:operatingr the clamp andv `the .electricalcontrol system .fof ...the

same are shown in Fig. l. A-reservoir'BDdcrthe hydraulic uid, usually oil, 1is connectedA byaline .3| to .the inletof the hydraulic ,pumpl32v drivenby thefelectric motor 33. The outlet of `thefpi'lmflzndelivers oil by line34 to the inlet .port.3.5 .of`oi1reversingvalye 3.6 which is hereoperated .bylsolenoid 3.1,. The oil'return line 38 .connects theoil return port 39 ofthe voil .reversing valve .tfc ,the linev 3| or equivalently to the reservoir`j30. f 'The Yhydraulic clamping cylinders 4D .are ,doublea'ctving .so .that application .of .hydraulic l.prssurefto one side of .the pistons 'therein eiectsth'e .clampingandto theotherside theclarnp releasina tion. l-lence, the lineAI, joining the-.ends .ofthe plied,` is `connected by line lditcthe vport 43, .while `thefclampingportlilll y, vto the .clamping orwork stroke-pressureenl'oLthe cylnders,. .jpin ed .by line 45, lby k.line `llgle'adirrg,to the'inlet port lllk of the check 4valve A1,38, .andline 4,9 fromthe. outletport of thechecklvalyeto line-45. The actuating pressure ,port 5I [offthe check valve sconnectedfby line 52 toa-pointin the circuit between `the*clampreleasing or return strokegpressureendof the cylinders and reversing valve `port 43, as here showrnto lineAI.. Y'IQ- the linesbetween-theoutlet portw50 of thecheckyalve and the clamping pressure .ends:oftheqc-ylinders, a pressure'switch 53 and pressure gauge- Mare connected. This switch is adjustablewith lrespect to the upper `and lower pressures Vof rits range of operation, sothat it opens when the clamping pressure attains a certainyalue'and closes'when The oil reversing-valvehas lfunctionrof.zre-

-versngzthe .directionof oilzrlow in the controlled 3 circuit, which is connected to the controlled ports 43 and 44 of the valve. Hence, the oil reversing valve is of that type, known to the art, which, at one operating position, internally connects inlet port 35 and controlled releasing port 43, while at the same time the controlled clamping port 44 is internally connected to the oil return port 39, and

at the other position reverses these connections, Y

inlet 35 to clamping port 44 and releasing port 43 to oil return port 39. n

The check valve is of that type which allows ow in one direction, here into inlet port 41 and out port 50, but not in the reverse direction unless actuating pressure is applied at port The actuating pressure applied at port 5| moves a'piston within the check valve which unseats the positively seating now checking means of the valve to allow reverse flow.

Pump motor 33 is shown connected to the negative terminal of a storage battery (not shown) by conductor III and to one side of the solenoid operated motor switch 2 by 'conductor I3. The other side of switch I I2 is connected to the positive battery terminal by conductor ||4 and also to one side of the solenoid I I5, which closes motor switch I|2 against the vopening bias of a spring. The oil valve solenoid, generally indicated 31, has two coils ||6 and I I1` by which the armature ||3 can be shifted forward and backward to move the oil reversing valve from a neutral position respectively to the clamping or releasing position. Spring means (not shown) are provided to urge the valve back to its neutral position. The other side of solenoid I I5 is connected by conductor I I9 to one side of both coils IIS and |I1. The other side of coil ||1 is connected by conductor |20 to pedal switch I 2| mounted on the truck at the operators control station. This pedal switchA is provided as a safety device so that the loadcant be released when the operator is off the truck. It is normally biased open, and is closed only by the operators foot when the operator is on the truck at the controls. thus serving as a type of "dead-man control for the clamp releasing circuit. The other side of coil ||6 is connected by conductor |22 to one terminal of the pressure switch 53.

The operating switches, namely, the clamping switch |23 and releasingswitch |24, are operationally related, so that when one is closed the Aother must be openiand vice-versa. Moreover,

the clamping switchv automatically locks in its closed position so that a positive unlocking action is necessary. These two switches |23 and |24 are usually incorporated-in one control device operf lfor releasing or opening the clamp,`and that switch |23 upon closure automatically locks, so that some positive action is necessary to release it. One Contact of each of these switches is connected by conductor |25 to conductor III. The other side of clamping switch |23 is connected to' pressureswitch 53 by conductor |26. The other side of the unclamping switch is connected by conductor |21 to the pedal-switch |2I.

` When-the clamping action of this hydraulic system is to be set in operation, clamping switch |23 is closed and is thereupon automatically held. The pressure switch 53 is closed, since no hydraulic pressure is yet developed. Hence there is a closed circuit from conductor ||4 coming from the positive battery`terminals over to conductor I I'I leading to the negative terminal of the battery, and the current flows from ||4 through motor switch solenoid I|5, conductor IIS, through the clamping control branch of the circuit, comprisng clamping coil I6 of the oil valve solenoid,

conductor |22, pressure switch 53, conductor |26, clamping switch |23, and conductor |25 to conductor I||. This current causes the closing of motor switch I2, so that the motor 33 and pump 32 come into operation. This same current also causes the clamping solenoid coil I|6 to throw the armature ||8 and so move the oil reversing valve to a position for clamping action, that is,

so that inlet port 35 connects to clamping port 44, and oil returnv port 39 is connected to release port 43. Thus the oildelivered bythe pump 32 to line 34 passes into port 35, through theY oil reversing valve and out port 44 to line 46 which carries it to the check valve inlet port 41. As the oil is flowing in the direction for which the check valve normally allows flow, the oil passes out through port 50 to line 49, and then to line 45 by which it is delivered to the clamping end of the hydraulic cylinders. As the pistons in cylinder 40 are moved in a work stroke for clampingaction by the oil admitted from line 45, oil on the other side of the pistons is expelled from the cylinders into linev 4|, whence it ilows through line 42 to releasing port 43, through the oil reversing valve to oil return port 39 and line 38, leading back to the line 3| joining oil tank 30 and intake of pump 32. The direction of arrows adjacent the hydraulic lines in Fig. 1 show the direction ofv oil flow during this institution of the clamping pressure.

When the desired clamping pressure is'attained in the cylinders, for which pressure switch 53 is pre-set, switch 53 opens, thereby interrupting the current now. Hence solenoidul I5 is de-energized allowing motor switch II 2 to open, so that motor 33 and pump 32 cease to operate. The armature |I8 of solenoid 31 moves from its neutral or nonoperative position only under the positive innuence of either coil IIIS or ||1 when energized. When current ceases to flow in one of these coils.

' the armature I I8, and therefore the connected oil reversing valve 36 is returned to the neutral position. When the pressure inthe system between the outlet of p'ump 32 and check valve inlet 41 drops on stopping of the pump, there is no back flow from .the clamping ends of cylinder 40 through lines 45 and 49, because of the checking action of the valve 48. Since this checking action prevents back flow of Oil from the clamping side of the pistons, the clamping pressure is thereby .maintained without needof continuous operation Lagain .moves the armature ||8 and valve 36 to .clamping position, and in solenoid I I5 the current flow closes switch I I2 to start the pump operating through the releasing control branchiof the Scircut,-.comprisiiigsdlerioiducoil Ill, conductor |20,

pedal switch |2I, conductor |21, switch, |24 and conductor |25, to reach conductor-l connectedy kvto motor33 4.and ltothe negative terminal -of vthe battery. This current flow energizes-:releasing 'pedal l' heaidofirpressurecoil l1 insolenoidl so that armature I I8 moves oil va1ve"3`6'away'frorn'neutralposition to the releasing position, wherein :inlet port lis connected .torreleasing .circuitry-(M1543, while` ampcircuit port 44 .is connectedt'o oil retur i138.; f'liecurrent iiowa'lsoienergizes solenni celos/ing motor .switch d i2, t'h'ereby starting Amotor iiand pumpl. .The oil now-iin the 'hydulic 4.strckeor clamping `action because of the change in oil switch position. Oil entering inlet port 35 now leaves clamp release circuit port 43 to traverse lines 42 and 4| to reach the clamp release pressure end of cylinders 4&3. The pressure in line 4| is communicated by line 52 to the inlet 5| of the check valve 48, causing the check valve to open to the reverse flow which it normally blocks. Now as the pistons in cylinders are moved in a return stroke to a releasing position by oil pressure in line 4|, oil is discharged from the cylinders on the other side of the piston into line 45, whence it goes into line 49, through the check valve 48, now open due to the action as above explained, through line 46 to clamping circuit port 44, through the oil reversing valve to oil return port 39, and so thereafter, as in the clamping action, back to the pump.

The pedal switch IZI is provided in the clamp opening control circuit as a safety measure. pedal switch is placed on the floor of the truck so that it can be closed only when the operator is This on the truck at his control or operating station..v

If the operator is not in such a position, but is off the truck, the roll cannot be released, even if the control lever of the operating switch is thrown so as to close switch |24` The previously explained clamping operation and control system maintains a sure clamping pressure, and that' except for pedal switch 2| on the truck floor- 1v and operating switches |23 and |24, which wouldl cal 6 b'munteeee the nuekf anni :easy rentr. :fthe operat The batteries, conductors' vIi2t'vam'i ,12.1

ofourseibefonthe"trukproper,while con- 'ftii'efilydf ulic'fline*s,-1witliy the labove exceptions, may Tco ned within-ftheclampfassembly f 'Themse the operate ffche'ck valve inthe ng yvalve .may bef-11s edfwhich Solenoid tolgiveiquickipositroicirfc t.Y tlieilcase "g otherfhydraiilily operated 'equipment .forifsuchservice 'fas stilting the upright frame icroperating ftheeloadzele- "conductor 1112i. '.coiildbe @connected gtozone 'sid'eficf switch |23 where conductor |26 is connected in Fig. l. To adjust the maximum clamping pressure, when the pressure switch is not used, an adjustable relief valve would be interposed in line 4B between clamping port 44 and check valve inlet 41 with an oil relief line to return released oil to the oil reservoir. Both conductors H9 and |25 could then be connected directly to the battery line. With such an arrangement, all the equipment concerned would be on the truck, with the exception of the cylinders 40 and check valve 48 which would of course be mounted in the clamp structure, with hydraulic lines 42 and 4G then being flexible connecting lines between truck and clamp.

I claim:

1. In a hydraulically operated mechanism hav-y ing a double-acting hydraulic cylinder and an electric motor powered pump and a fluid reversing valve for reversing the direction of fluid ow with :respect to the cylinder, an electrical control systemcomprising a solenoid operated motor switch in series with the motor and the source of electrical power therefor; solenoid means for operating the fluid reversing valve, said means comprising an armature mechanically linked to said valve and two connected coils for moving said armature to each of two operating positions for the valve; and an electrical circuit immediately connected to the electrical power source, said circuit comprising in series a solenoid coil to close said motor switch and a work stroke control branch and a return stroke control branch, said branches being connected to said power source, in parallel relation to each other, said work stroke control branch including in series one coil of said solenoid means and a work stroke `control switch, said return stroke control branch`Vv |14 12in and 12- .may benexibie Were fa check'zvallve :not

the second coil. of said solenoid means -turn stroke control switch. l

aerien 7 v. including in series the second coil of said sderxoid meansy and a return stroke control switch. A I, c

2.- Inva hydraulically operated mechanism having a double-acting hydraulic cylinder and anielectric motor powered pump anda vduid re- 'versingvalve for reversing the direction o1' fluid ilow with respect to the cylinder,v an electrical control'system comprising a solenoid operated motor switch in series with the motor and the electrical power source therefor; solenoid means for operating the iiuid reversing valve, said means comprising an armature mechanically linked to said valve and two connected coilsfor moving said armature to each of two operating positions for thevalve; and an electrical circuit immediately connected across the electrical powersource, said circuit comprising in series. a

vsolenoid coil to close saidmotor'switch anda work stroke controlfbranch and a return stroke control branch, said branches being in parallel noidimeans, a pressure actuated switch responsiv'e to the work strokerpressure in said hydraulic cylinder and a work stroke control switch, said return stroke control branch including in series vand a re- 3. In a hydraulically operated vroll clamping 'mechanism foran industrial tier lift truck, having a hydraulic clamping cylinder vand an electric motor poweredA pump and a' fluid reversing valve for reversing the direction of; fluid flow with respect to the cylinder, anelectrical control power source therefor; solenoid means for operl ating the :duid reversing valve, said means com- ,prising an armature mechanically linked to said iile of this patent:

valve and two connected. coils for moving said amature to eachof two operating positions for the valve; andan electrical circuit inmediately connected to said power source. said circuit compris/ing in series Va solenoid coil to close said motorswitch and a clamping control branch and a. release control branch. said branches being Yin parallel relation to each other, said clamping b ranch including in series one coil of said solenoid means, a, pressure actuated switch responsive to the clamping pressure in said hydraulic cylinder and a clamping control switch, said release control branch including in series the second coil of said solenoid means, a normally open pedal switch mounted at the operators station to be held closed by the operator, and a release control switchsaid pressure switchl being adjustable to open at one pressure and close at a lower pressure. 1

' 'f JOSEPH A. ACKERMANN.

. REFERENCES CITED 'The following references are of record in the UNITED s'rATEs'PATEN'rs l Number Name Date 1,616,841 Beebe Feb. 8, 1927 1,955,154 Temple Apr. 17, 1934 2,209,565 Harris et al July 30, 1940 2,219,896 Harrington et al. Oct. 29, 1940 2,283,271 Loomis May 19, 1942 2,382,263 Schnell Aug. 14,1945 2,449,639

Cannon Sept. 21. 1948 

